How to tell if your shower was waterproofed right

Most shower failures we get called about have nothing to do with the tile. The tile looks fine. The problem is behind it.

Grout is not waterproof

This surprises people: water is supposed to get through grout. Grout is cement — it absorbs water. In a properly built shower, that’s fine, because the waterproofing isn’t the grout or the tile. It’s a membrane behind them, sloped so that anything getting through drains out instead of soaking the wall.

A shower without that membrane works fine on day one. It usually works fine in year one. Somewhere between year three and year six, the framing behind the wall has been damp a few hundred times, and you find out the hard way — a soft spot in the floor, a stain on the ceiling below, a musty smell that won’t leave.

What a properly built shower has

• A continuous waterproof membrane over the walls and pan — we use the Schluter Kerdi system
• A bonded-flange drain that connects to the membrane directly, so there’s no seam to work loose
• A sloped pan under the membrane, not just a sloped tile surface
• Flat, properly prepped substrate — mud work or self-leveling before any tile goes down

None of it is visible when the shower is finished. That’s the frustrating part for a homeowner comparing bids: the $2,000-cheaper quote looks identical on the surface.

Warning signs in an existing shower

• Grout lines that keep cracking or crumbling in the same spots
• Tiles that sound hollow when you tap them
• A musty smell that comes back after cleaning
• Discoloration on the wall or ceiling on the other side of the shower
• Caulk that won’t stay sealed where the walls meet the pan

One of these alone isn’t proof. Two or three together usually mean water is getting somewhere it shouldn’t.

What to ask a contractor before they build yours

1. What waterproofing system do you use — and is it a membrane, or just a coating on the backer board?
2. How does the drain connect to the waterproofing?
3. Do you do your own floor prep and mud work, or tile over what’s there?

A tile setter who builds showers properly will answer all three without blinking. If the answer is “we use waterproof board” and nothing else, keep asking questions.

AMC Custom Tile has installed tile in the Kansas City area since 2002. Every shower we build is waterproofed with a Schluter Kerdi system and an integrated drain. If you’re planning a shower or worried about the one you have, call Tony at 913-269-1212.